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Part 4: Technical Reference
BJC-4400
2) Printer controller (IC3)
The printer controller contains the interface controller, print head controller, buffer controller, DRAM
controller, EEPROM controller, I/O ports, etc. It operates in synchronization with an external 22.11
MHz external clock input.
Interface controller
The interface controller receives from the computer, 8-bit parallel data which is synchronized with the
data strobe pulse (STROBE) through the BUSY/ACKNLG handshake. It also controls other interface
signals.
The data received through the interface is stored in the DRAM's receive buffer and analyzed by the
MPU.
When the printer initialization signal INIT is input through the interface to the printer controller, the
printer controller outputs a BUSY signal. Also, after INT1 is output to the MPU and print data in the
print buffer is printed, the printer is initialized.
DRAM controller
The DRAM controller is a DRAM-specific bus separated from the MPU bus. It controls the 4 M bit
DRAM's 10-bit address/16-bit data bus and also executes read/write control, RAS/CAS control, and
refresh control.
Buffer controller
The buffer controller automatically writes the received data to the receive buffer on the DRAM,
manages the receive buffer's remaining capacity, automatically reads the print buffer, and clears the data
after it is read.
Print head controller
The print head controller converts the print data read from the DRAM's print buffer from parallel to
serial and sends it to the print head. At the same time, the printed dots are counted for the variable
control of the Heat-enable (H ENB) signal pulse width.
The head-driving signals consist of the block enable signals (B ENB 1, 2, 3), odd/even enable signals
(OddENB/EvenENB), and heat enable signals (H ENB 0, 1, 2, 3). The block enable signals and
odd/even enable signals specify the block for time-shared drive. The heat enable signals control the
eject heater's conduction time.
I/O port
The I/O ports sense the RESUME and CARTRIDGE buttons' input status. The output ports control
the lighting of the POWER and ERROR indicators.
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